~Secondary skill is an additional option you can get from Legendary equipments, you can obtain Legendary equipments by:~

A.) Forging shards or pieces of Legendary weapons~Finishing all the ‘Goals’ / Achievement quests gives a player the chance to forge a Legendary weapon using the 7 pieces of the weapon given as reward.
~Level 90 legendary weapon, armor, and accessories’ shards can be obtained in Silent Temple (unlocked when Heavenly Peak level 60 is cleared).